Parachute release mechanism

ABSTRACT

The mechanism includes first and second chambers each of which continuously communicates with the ambient space through a small opening. The sizes of the chambers, and the sizes of the openings, are such that a predetermined relationship is maintained between the pressure in the first chamber and the pressure in the second chamber, regardless of the rate of climb or fall. Preferably, the predetermined pressure relationship is such that the pressures in the two chambers remain equal to each other. The sizes of the chambers and of the openings are also determined in such manner as to satisfy other conditions. An aneroid is provided to effect opening of a relatively largediameter port between one of the chambers and the ambient space when a set altitude is reached. A diaphragm is provided between the two chambers and is responsive to the differential in pressure therebetween, created by the aneroid, to actuate the parachute release. Trigger and latch means associated with the diaphragm are adapted to cause reliable triggering in response to relatively low pressure differentials, and without danger of spurious actuation. The small openings between the chambers and the ambient space are capillary passages. The size of the diaphragm is small in comparison to chamber volume.

United States Patent Jones PARACHUTE RELEASE MECHANISM [72] Inventor: Leon Jones,-11332 Pemberton Rd.,

Los Alamitos, Calif. 90720 22 Filed: Sept.2l, 1970 211 Appl. No.: 74,004

52 US. Cl ..'.....244/149, 244/150 51 Int. Cl ..B64d 17/56, 864d 17/58 58 Field of Search ..244/149, 150; 74/2 [56] References Cited UNITED STATES PATENTS 3,547,383 12/1970 Carpenter, Jr ..244/150 3,468,502 9/1969 Kinney ..244/15o 3,291,424 12/1966 Hatfield a a1. ..244/149 OTHER PUBLICATIONS Parachutist Magazine, PO. Box 109 Monterey, Calif. 93940, March 71, pages 18 and 19.

Parachutist Magazine, PO. Box 109 Monterey, Calif. 93940, November 1969, Pages 25 Para-Gear Equip Co., 5138 N. Broadway, Chicago, 111., 1968 Mini-Catalog, page 3 Primary Examiner-Milton Buchler Assistant Examiner-Carl A. Rutledge Attorney-Gausewitz, Carr & Rothenberg 1 1 Sept. 12, 1972 [57] ABSTRACT The mechanism includes first, and second chambers each of which continuously communicates with the ambient space through a small opening. The sizes of the chambers, and the sizes of the openings, are such that a predetermined relationship is maintained between the pressure in the first chamber and the pressure in the second chamber, regardless of the rate of climb or fall. Preferably, the predetermined pressure relationship is such that the pressures in the two chambers remain equal to each other. The sizes of the chambers and of the openings are also determined in such manner as to satisfy other conditions. An aneroid is provided to effect opening of a relatively largediameter port between one of the chambers and the ambient space when a set altitude is reached. A diaphragm is provided between the two chambers and is responsive to the differential in pressure therebetween, created by the aneroid, to actuate the parachute release. Trigger and latch means associated with the diaphragm are adapted to cause reliable triggering in response to relatively low pressure differentials, and without danger of spurious actuation. The small openings between the chambers and the ambient space are capillary passages. The size of the diaphragm is small in comparison to chamber volume.

14 Claims, 9 Drawing, Figures PATENTEDSEPIZIHTZ 3.690.605 sum 1 0:3

INVENTOR. L 0A/ JONES PATENTEDSEP 12 I972 SHEET 2 BF 3 fig. Z

2 4 1 a #4 4 if 4 v l L 45 W i 3' Pill; 4: 47 V/ i J/ a? I r I 5f {0} 17/ If 2; V6 49 INVENTOR. 450M JONES.

PARACHUTE RELEASE MECHANISM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates 'to the field of automatic mechanisms for effecting release of parachutes at preset altitudes, and/or when the parachutist has dropped a specified distance from the airplane.

2. Description of Prior Art The prior art contains numerous parachute release mechanisms of a type wherein an operation must take place immediately prior to egress of the parachutist to the prior art, are frequently characterized by the presence of explosive devices, batteries, and other expensive and single-use mechanisms which require maintenance between firings in order to perform satisfactorily. The parachute release mechanisms of the prior art are frequently bulky, complex, and relatively inaccurate in operation. Relative to the latter factor, it is emphasized that, in mechanisms wherein the aneroid must directly operate a latch or the like, there is a considerable amount of friction which prevents achievement of the highest degree of accuracy relative to the altitude at which the parachute will open.

Various prior-art parachute release mechanisms are taught by the following US. Pat. Nos. 2,743,891, 2,937,831, 2,960,297, 3,013,834, 3,142,958, and 3,291,424. Another US. Pat. No. 2,923,160, does not relate to a parachute release but shows a diaphragm operated escapement mechanism.

SUMMARY OF THE INVENTION The present mechanism comprises first and second chambers each in restricted communication with the ambient space, and so constructed that a predetermined relationship will be maintained at all times between the pressures in such first and second chambers. The degree of constriction of the opening between each chamber and the ambient space is caused to be such that an operating pressure differential will be built up, between each chamber and the ambient space, when the parachutist is falling at such velocity that it is desired that the parachute be opened. An aneroid valve mechanism effects sudden and relatively free communication between one of the chambers and the ambient space when the set altitude, namely the desired parachute-opening altitude, is reached, thus suddenly creating an operating pressure differential between the two chambers. Means responsive to such differential are provided to release the parachute.

The pressures in the two chambers should be equal until the aneroid operates. The relationships are such that the operating pressure differential will be achieved, when the aneroid valve is open, after a few hundred feet of fall, so that the mechanism functions properly even when egress from the aircraft occurs below the set altitude.

Stated in greater detail, a diaphragm is provided between the two chambers and responds to any operating pressure differential therebetween, and trigger and latch means are associated with the diaphragm to release the parachute when the operating pressure differential results. The diaphragm is relatively small in diameter, in comparison to the volume of, either chamber. The trigger and latch mechanism includes cam means to insure against spurious operation. The restricted communications between the chambers and the ambient space are through capillary passages.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of .a parachute release mechanism embodying the present invention;

FIG. 2 is a longitudinal sectional view on line 22 of FIG. 1;

FIG. 3 is a horizontal sectional view on line 3--3 of FIG. 2, as viewed in the direction of the arrows;

FIG. 4 is a longitudinal sectional view on line 4-4 of FIG. 2, asviewed in the direction of the arrows, and showing the mechanism in its cocked condition;

FIG. 5 is a view corresponding to FIG. 4 but showing the mechanism after release;

FIG. 6 is a transverse sectional view on the broken line 6-6 of FIG. 4;

FIG. 7 is a schematic representation of the trigger and latch mechanism; 1

FIG. 8 is an enlarged fragmentary sectional view on line 8-8 of FIG. 4; and 1 FIG. 9 is an enlarged fragmentary sectional view on line 99 of FIG. 4.

GENERAL DESCRIPTION OF A PREFERRED EMBODIMENT Stated generally, the parachute release mechanism comprises housing or casing means 10 to define a first chamber 11 and a second chamber 12. Chambers 11 and 12 are associated, respectively, with means 13 and 14 to effect restricted communication between the chambers and the ambient space. Such restricted communication means are shown in FIG. 3 as being capillary tubes. A pressure-responsive valve means 15 (FIG. 1) is provided to effect relatively unrestricted communication between the first chamber 11 and the ambient space when the parachutist or jumper falls to a set altitude. Such pressure-responsive valve means includes an adjustable aneroid valve mechanism (FIG. 1) which connects through tube means 16 with the first chamber 11 as shown in FIG. 3.

Diaphragm means 17 are provided and are responsive to the pressures in the first and second chambers 11 and 12, respectively, to operate a trigger and latch mechanism 18 (FIG. 7), when a predetermined pressure differential exists between such chambers. Trigger and latch mechanism 18, in turn, is associated with a spring release means 19 adapted to effect pulling of the rip cord which causes opening of the parachute, the latter being schematically represented at 20 in FIG. 1.

The pressure-responsive or aneroid valve mechanism 15, which may be of various types known in the art, is a relatively frictionless mechanism which maintains relatively large-opening communication between tube means 16 (and thus chamber 11) and the ambient atmosphere at all times when the mechanism is at an elevation below the altitude at which it is desired that the parachute open. Conversely, the valve closes off the tube 16 (completely) when the mechanism is above the altitude of parachute opening. Such altitude at which it is desired that the parachute open is referred to as the set altitude.

The chambers 11 and 12, and the restricted communication means 13 and 14 (FIG. 3) associated therewith, are constructed (and are correlated to diaphragm means 17 and its associated elements) in the following manner:

.(a) The relationships are caused to be such that, at all times when the aneroid valve 15 (FIG. 1) is closed, and regardless of the rate of climb or fall, the pressure in chamber 11 will bear a predetermined relationship to the pressure in chamber 12. Very preferably, the predetermined relationship is such that the pressure in chamber 11 is always equal to that in chamber 12 when aneroid valve 15 is closed. This is preferably accomplished by making chamber 11 have the same volume as chamber 12, and by making the length and diameter of the restricted communication means 13 the same as the length and diameter of the restricted communication means 14. It should be understood,,however, that the chambers may have different volumes if the restricted communication means 13 and 14 are correspondingly adjusted. Throughout the remainder of this specification, it will be assumed that the relationships are such that the pressure in chamber 11 is always equal to that in the chamber 12 when the aneroid valve 15 is closed.

(b) The relationships are caused to be such that the pressure in each of chambers 11 and 12 will, after the parachutist has dropped a predetermined distance from the aircraft, be sufficiently low that the diaphragm means 17 will operate in response to an open condition of aneroid valve 15 (FIG. 1). When the parachutist egresses from the aircraft more than such predetermined distance above the set altitude, as is normally the case, the diaphragm means 17 will operate to effect opening of parachute 20 as the parachutist drops through the set altitude. When the parachutist egresses from the aircraft at an elevation below the set altitude, or at an elevation less than the predetermined distance above the set altitude, the diaphragm means 17 will operate to open the parachute 20 after the parachutist has dropped the predetermined distance from the aircraft. Such predetermined distance is, preferably, caused to be approximately 200 feet. The predetermined distance is always caused to be sufficiently great that the parachute, when it opens, cannot be caught on the aircraft.

(c) The relationships are caused to be such that, regardless of the open condition of the aneroid valve 15, there can never be a sufficient pressure differential across diaphragm means 17 to effect opening of parachute 20 when the parachutist is falling at less than what may be termed dropping velocity. Such dropping velocity" is determined in accordance with various factors, including (for example) whether the device is being used for sport parachuting or for military parachuting. Relative to sport parachuting, for example, the dropping velocity may be on the order of 25 feet per second when the parachute 20 is the reserve chute, not the main one. Such relatively low value may be selected because it is not desired that the reserve chute open when the parachutist is being supported by the main chute in opened condition, but it is desired that the reserve chute open when the parachutist is dropping at a relatively low velocity due to the fact that the main chute is streaming behind him in tangled condition. For various other uses, for example in many forms of military use, the dropping velocity" may be much higher, such as feet per second.

In addition to the above considerations, it has been discovered, contrary to expectations, that the area of the diaphragm means 17 should be relatively small in comparison to the volume of each chamber 11 and 12, so that operation of the diaphragm does not effect an undue percentage variation in the effective volumes of the associated chambers.

The following is a description of the operationof the parachute release mechanism as thus far described, and with particular reference to sport parachuting wherein the present mechanism is associated with the reserve chute only. While the parachutist is still on the ground, he sets the aneroid valve mechanism 15 (HO. 1) so that it will open at the desired set altitude (above sea level). Thus, if the elevation of the ground (above sea level) is l,000 feet, and the parachutist desires that the parachute open 1,500 feet above the ground, he sets the aneroid valve mechanism 15 to operate at 2,500 feet above sea level. It is an important advantage of the present invention that such setting is made on the ground, when the parachutist is not in any excited or panicked condition, and that (except relative to certain unusual conditions as stated below) no operations need occur in the aircraft prior to the jump.

The airplane containing the parachutist is then flown up to the desired altitude at which egress is to occur. When the plane climbs through the set altitude, there is no release of the mechanism. This is true for two reasons, namely: (a) the airplane normally climbs through the set altitude at a rate of climb below the dropping velocity, and (b) even if the rate of climb is greater than the dropping velocity, any pressure differential between chambers 11 and 12 is in such direction as to prevent operation of the diaphragm means 17. Referring to FIG. 6, it is pointed out that the chamber 11 communicates through passage means 21 with the upper side of diaphragm means 17, and that chamber 12 communicates through passage means 22 with the lower side of diaphragm means 17. During climb to the set altitude, the aneroid valve 15 is open,

thus causing the pressure in chamber 12 to be higher than that in chamber 11 (since the latter pressure can bleed faster as ambient pressure decreases). As described below, the diaphragm means operates when the pressure in chamber 11 is higher than that in chamber 12. It does not operate when the reverse condition occurs.

After the aircraft has climbed to the elevation (far above the set altitude) at which the jump is to occur, the parachutist merely egresses and then manually opens his main chute at any desired elevation above set altitude. If, for any reason, the main chute is not open by the time the chutist drops to the set altitude, opening of aneroid valve at the set altitude causes a relatively trigger and latch means 18 (discussed below) to open the reserve parachute.

If, on the other hand, there is no emergency and the main chute opens (as is normally the case) well above the set altitude, there is no opening of the reserve chute when the parachutist passes through the set altitude due to the fact that the rate of falling is then less than the dropping velocity" defined above. In the latter event, the parachutist merely falls to earth using the main chuteonly.v e

- The low velocity of fall (below dropping velocity), after the main chute opens, allows the air pressures in chambers 11 and 12 to remain nearly equal to ambient pressure as. the latter increases. Therefore, when the aneroid valve 15 opens at set altitude, the resulting increased pressure in chamberll is not sufficiently great to permit the diaphragm means 17 to overcome the resistance of a calibrated helical compression spring S shown in FIGS. 2 and 6. The diaphragm means 17 therefore cannot operate the trigger and latchmeans 18, FIG. 7, and the reserve chute does not open.

. In the event that (prior to the time of egress) the aircraft passes downwardly through the set altitude, there is no openingof the parachute due to the fact that the rate of descent of the aircraft is normally far lower than the above-defined dropping velocity." In the unusual situation where the pilot of the aircraft desires to indulge in acrobatics or to dive through the set altitude, the parachutist is instructed to reset the aneroid valve 15 to a new set altitude far lower than that at which the aircraft is flying. It follows that the aneroid never opens and that the parachute will not release in the aircraft. Prior to the time a jump is desired, and after the acrobatics have ended, the parachutistresets the mechanism 15 to theoriginal set altitude and makes his jump.

The present parachute release mechanism is especially applicable to helicopters, such as military helicopters, and which do not change altitude rapidly. Therefore, the dropping velocity defined above may be made low and still assure that no undesired release of the parachute will occur despite the fact that the chutist is not required to make any setting or take any action prior to the jump. Particularly in the case of helicopters, it is convenient to set the aneroid valve mechanism 15 for an elevation higher than that at which the helicopter ever flies. It follows that the present mechanism will effect opening of the parachute 20 after the parachutist has fallen the above-indicated predetermined distance (such as 200 feet) from the helicopter.

The present mechanism is readily employed on military jet aircraft and other fast-diving planes, by introducing in the tube means 16 a valve mechanism which is operated by a pin or other device immediately prior to the jump. The pin may be automatically pulled as the pilot ejects. Such valve mechanism (not shown) blocks flow of air through the tube 16 at all times prior to pulling of the pin. In additionto such unshown valve mechanism, and for applications such as for rapidlydiving jet planes, suitable valves may be associated with each of chambers 11 and 12 toassure that such chambers remain at ambient at all times despite dives, etc.. made by the jet. Immediately prior to the jump, such valve means are operated (again as by a pin) to closed positions whereupon the restricted communication means 13 and 14 become operative.

One of the numerous advantages of the present mechanism is that the set altitude: may be accurately determined. The aneroid 15 includes, as above stated, a relatively frictionless valve element which is to be contrasted with a relatively high friction release or latch mechanism. Since friction is minimized in the present parachute release device, the set altitude may be accurately determined. Other major advantages include, as

DETAILED DESCRIPTION The, housing or casing means 10 is illustrated tocomprise a central element 23, which is preferably a die groove or chevron edges) being such the edge caps are mounted in sealing manner. The central housing element 23 and the edge caps 26 define the first and second sealed chambers 11 and 12 and which have equal volumes.

In addition to the central element 23 and the edge caps 26, the housing. or casing means 10 comprises a central insert 27 which is secured to element 23 by screws 28. The above indicated diaphragm means 17 is provided in a recess in the underside of insert 27. Such diaphragm means includes a flexible diaphragm 29 formed of elastomeric material and to which a relatively rigid plate 30 is attached. A screw 31 extends through thediaphragm 29 and plate 30 and into an actuating post 32. Such post, in turn, extends slidably through a support disc 33 which is secured to insert 27 (snugly in the recess therein) by screws 34 shown in FIGS. 4 and 5. The above-mentioned helical compression spring S seats between plate 30 and disc 33.

When the diaphragm 29 bows downwardly, due to the presence of a relatively high pressure inchamber l1 and which is communicated through passage means 21 (FIG. 6) to the upper side of the diaphragm, the post 32 also moves downwardly and pushes the end of a flexible trigger 36 to a point below the end of a stop pin 37 whereby the trigger is released. Trigger 36 is a flexible thin metal bell crank lever pivoted at 38 to insert 27 and having a notch 39 therein. The trigger 36 is biased in a clockwise direction, as viewed in FIGS. 4 and 5, by a spring 40 which is relatively weak in comparison with a spring (indicated below) which biases an associated latch member.

The trigger 36 and related parts cooperate with a latch member 41 in forming the trigger and latch mechanism 18 indicated above. The latch member 41 is an elongated element which is pivoted at 42 to insert 27. An upstanding lug 43 at the distal end of latch member 41 is disposed in notch 39 when the mechanism 18 is in the latched or cocked position of FIGS. 4 and 7. Formed in one edge of latch 41, relatively adjacent pivot 42, is a notch 44 which receives (when the mechanism is cocked as shown in FIGS. 4 and 7) a piston pin 46 associated with the spring release means 19.

The piston pin 46 extends downwardly through a slot 47 (FIGS. 2 and 6) in central housing element 23 for fixed connection to a hollow piston 48. Such piston 48 slides in a longitudinal bore 49 in housing element 23 under theaction of a helical compression spring 50 therein. When the piston 48 is permitted to slide, due to the releasing operation of trigger and latch mechanism 18, it moves from the cocked position shown in FIGS. 2 and 3 to a release position in engagement with a rubber bumper 51 (FIGS. 2 and 3) at the end of bore 49. This effects pulling of a cord '52 which extends to the parachute 20 (FIG. 1) to open the same.

In the operation of the trigger and latch mechanism 18 and spring release means 19, the parts are originally in the cocked position shown in all figures except FIG. 5. An edge of trigger 36is thus stopped by stop pin 37, whereby the lug 43 is maintained in notch 39 to prevent movement of piston pin 46 and thus of piston 48, pin 46 then resting against an edge of notch 44 of the latch 41.

To insure against accidental shifting of the end of trigger 36 to a position beneath the lower end of pin 37, a cam means 53 (FIGS. 4, 5 and 9) is provided in the form of the head of a screw which extends into support disc 33. The end of trigger 36 rests below the cam means 53 and therefore cannot jump downwardly despite any dropping or other jarring of the mechanism.

The above-indicated downward movement of the diaphragm means 17, when the pressure in chamber 11 is sufficiently above that in chamber 12, operates through the post 32 to shift trigger 36 below the lower end of stop pin 37 (FIG.' 8). This operation is accompanied by flexing of the distal end of the trigger 36 because a portion of the trigger is held relatively stationary (against flexing) by the cam means (screw head) 53 (FIGS. 4, 5 and 9). The resulting release of latch 41 permits the same to be thrown, due to the action of spring 50 and piston pin 46, in a clockwise direction as shown in FIG. 7 and counterclockwise as shown in FIGS. 4 and 5. The trigger 36 pivots clockwise from the position shown in FIG. 4 to that shown in FIG. 5, due to the operation of both of springs 50 and 40.

The latch 41 is thrown counterclockwise (as stated above) from the position shown in FIG. 4 to approximately the position shown in phantom lines in FIG. 5, due to the fact that the piston pin 46 engages latch 41 alonga line of force which is a predetermined small moment arm from the pivot pin 42 for the latch 41. Also, the edge of notch 44 which is engaged by piston pin 46 is somewhat inclined. The counterclockwise pivoting of the latch 41 permits release of piston pin 46 so that the same suddenly shifts and permits the piston 48 to shift into engagement with bumper 51, thereby pulling on cord 52 and opening the parachute.

After the latch 41 reaches the instantaneous position shown in phantom lines in FIG. 5, it pivots clockwise (FIG. 5) under the action of a spring 45 until the distal I end of the latch engages the piston pin 46 as shown in solid lines in FIG. 5. The trigger 36 remains in the indicated clockwise pivoted position, due to the operation of the spring 40. It is to be noted that the piston pin 46 only operates on the latch 41, and not on the trigger, since the upper end of the piston pin is, as shown in FIGS. 2 and 6, beneath the plane of the trigger 36. The parts remain in the released position shown in solid lines in FIG. 5 until recocking of the mechanism as stated below.

It is a feature of the invention that recocking may be effected by merely pulling on the cord 52 until the latch automatically resets. Such pulling compresses the spring 50 and causes the piston pin 46 to move to the left from the position shown in FIG. 5 (to the right as viewed in FIG. 7). Movement to the left causes the piston pin 46 to slide along the edge of latch 41 and thereby cam such latch 41 counterclockwise, as viewed in FIG. 5, almost to the position shown in phantom relative to latch 41. When the piston pin 46 reaches notch. 44, such camming action abruptly ceases and permits the spring 45 to pivot latch 41 clockwise until the lug 43 engages an edge of trigger 36. Spring 45 is caused to be stronger than spring .40, so that the engagement of lug 43 with the edge of trigger 36 causes counterclockwise movement of the trigger (FIG. 5) until the lug 43 is again disposed in trigger notch 39 and the apparatus is cocked as shown in FIGS. 4 and 7. It is then no longer necessary to pull on cord 52, and upon release thereof the piston pin 46 will engage the edge of notch 44 as shown in FIGS. 4 and 7.

During the described recocking of the trigger and latch mechanism 18, the end of trigger 36 cams beneath the bottom of stop pin 37 (FIG. 8), this being permitted because the leading edge of the trigger (the one shown in the right in FIG. 8) is spaced farther below the lower surface of support disc 33 than the degree of downward protrusion of the stop pin 37. The indicated camming action is accompanied by a flexing of the trigger 36, which is relatively flexible. Such flexibility of the trigger assures that the trailing edge (during recocking) will snap to the locking position shown in FIG. 8 and will therefore assure against accidental discharge. Furthermore, the cam means 53 (FIG. 9) operates as above described to insure that even a dropping of the apparatus will not permit inadvertent shifting of the trigger 36 beneath stop pin 37.

The distal end of the flexible trigger 36 is twisted, as viewed in FIG. 8, in such manner that it will cam or ride beneath pin 37 as described.

It is a feature of the invention that the amount of diaphragm movement and the travel of post 32 is very small. The pin 37 only protrudes about 0.008 inch below the lower surface of disc 33, whereby a travel of only 0.008 inch is necessary to shift the trigger 36 beneath the pin 37 (FIG. 8).

Proceeding next to a description of the restricted communication means 13 and 14, these are illustrated to comprise capillary tubes the ends of which are flanged and seated in suitable recesses in the central portion 23 of the housing or casing. Suitable seal means, not shown, are provided to insure against any ingress or egress of air relative to chambers 11 and 12 except through the capillary tubes 13 and 14 (prior to the time aneroid valve 15 opens). Such sealing means are provided not only around the flanges at the outer ends of the tubes, but also around the piston or plunger 32 and around the joints or connections in passage means 21 and 22 (FIG. 6).

The lengths and diameters of the passages in capillary tubes 13 and 14 are carefully selected, relative to the volumes of chambers 11 and 12, to provide the effects stated in detail inthe early portions of this specification. For example, in the case of the illustrated housing or casing means which is approximately 6 inches long by 3 inches wide by 1% inches high (external dimensions), each of the capillary tubes may have a bore therethrough the diameter of which is 0.0010 inch. The length of each tube may be two inches. By employing long tubes, the manufacturing of the device is greatly facilitated and, furthermore, the passages may be of larger diameter while still achieving the desired degree of restriction.

Suitable screens 54(FlG. 3) are provided to dirt from entering the capillary tubes.

The diameter of the diaphragrn29 is, as stated above, small in comparison to the volume of each chamber 11 and 12. Relative to the specific example given in the preceding paragraphs, the diaphragm 29 may have a diameter of 1% inches. It has been found, surprisingly,

prevent that a small diaphragm actually increases the sensitivity of the apparatus, as distinguished from decreasing the sensitivity thereof.

The flexible trigger 36 is bent in such manner that the free end thereof is biased against the inner surface of disc 33, except during periods when the trigger rides over pin or stop 37.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

What is claimed is:

l. A parachute release mechanism, which comprises:

wall means to define first and second chambers,

restricted communication means to effect restricted communication between said first chamber and the ambient atmosphere and to effect restricted communication between said second chamber and the ambient atmosphere, the volumes of said first and second chambers, and

the flow characteristics of said restricted communication means, being such that a predetermined relationship is maintained between the air pressure in said first chamber and the air pressure in said second chamber as the parachute release mechanism falls through the atmosphere,

the volumes of said first and second chambers, and

the flow characteristics of said restricted communication means, also being such that the falling of the parachute release mechanism through the atmosphere at at least a predetermined dropping velocity for at least a predetermined distance effects predetermined lowering of the air pressure in said first chamber relative to the air pressure of the ambient atmosphere, and also effects predetermined lowering of the pressure-responsive valve means to effect relatively unrestricted communication between said first chamber and the ambient atmosphere when the parachute release mechanism is at a predetermined set altitude, and

mechanical actuating means responsive to the increased pressure in said first chamber, upon opening of said pressure-responsive valve means after dropping of the parachute release mechanism to said set altitude, and also responsive to achievement of said predetermined lowering in the air pressure in said second chamber, to effect opening of a parachute.

2. The invention as claimed in claim 1, in which said predetermined relationship, maintained between the air pressure in said first chamber and the air pressure in said second chamber, is such that said actuating means will not operate when said pressure-responsive valve means is in closed condition, and in which said pressure-responsive valve means is in closed condition when above said set altitude, and is in open condition when below said set altitude.

3. The invention as claimed in claim 1, in which said predetermined relationship, maintained between the air pressure in said first chamber and the airpressure in said second chamber, is such that the air pressure in 7, said first chamber is maintained substantially equal to the air pressure in said second chamber while said mechanism is dropping through the atmosphere, in which said actuating means comprises a diaphragm one side of which is exposed to the air pressure in said first chamber, and the other side of which is exposed to the air pressure in said second chamber, and in which resilient means are provided to prevent operation of said diaphragm unless the pressure in said first chamber is a predetermined amount greater than the pressure in said second chamber.

4. The invention as claimed in claim 1, in which said pressure-responsive valve means is closed at all altitudes above said set altitude, and is open at all altitudes below said set altitude, wherebyto effect relatively unrestricted communication between the am air pressure in said second chamber relative to t the air pressure of the ambient atmosphere,

bient atmosphere and said first chamber at said set altitude and at all altitudes lower than said set altitude, and in which said restricted communication means comprises a first capillary passage extending directly between said first chamber and the ambient atmosphere and further comprises a second capillary passage extending directly between said second chamber and the ambient atmosphere.

5. The invention as claimed in claim 1, in which the volume of said first chamber is substantially equal to the volume of said second chamber, in which said restricted communication means: comprises a first capillary passage extending directly between said first chamber and the ambient atmosphere and further comprises a second capillary passage extending directly between said second chamber and the ambient atmosphere, and in which the flow characteristics of said first capillary passage are substantially equal to the flow characteristics of said second capillary passage.

6. The invention as claimed in claim 1, in which the volumes of said first and second chambers, and the flow characteristics of said restricted communication means, are such that the falling of said parachute release mechanism through the atmosphere at a velocity less than said predetermined dropping velocity does not effect said predetermined lowering of the air pressures in said chambers, and therefore does not result in operation of said actuating means upon operation of said pressure-responsive valve means at said set altitude, regardless of the distance of dropping.

, 7. The invention as claimed in claim 1, in which said predetermined distance is at least sufficiently great to insure that said parachute will not be caught on the aircraft.

8. The invention as claimed in claim 1, in which said pressure-responsive valve means is an aneroid valve.

9. The invention as claimed in claim 1, in which said actuating means comprises a trigger, a latch operated by said trigger, a compressed spring released in response to operation of said latch, and a diaphragm means one side of which communicates with said first chamber and the other side of which communicates with said second chamber, said diaphragm means being adapted to operate said trigger.

10. The invention as claimed in claim I, in which said actuating means includes a diaphragm the diameter of which is small in comparison to the volumes of said chambers, one side of said diaphragm communicating with said first chamber, the other side of said diaphragm communicating with said second chamber, and means operated by said diaphragm to effect opening of said parachute.

11. A release mechanism, which comprises:

a housing,

a stop provided in said housing,

a trigger pivotally mounted in said housing for pivotal movement about a predetermined axis, at least one end of said trigger being flexible,

at least part of said one end of said trigger being inclined,

said inclined part of said one end being adapted when said trigger is pivoting in a mechanismcocking direction to cam relative to said stop to thereby flex said trigger end and permit trigger movement to a cocked position against one side of said stop,

a latch operably associated with said trigger for retention thereby when said trigger is in said cocked position, controlled means operably associated with said latch for operation thereby, and

operating means to push against said one end of said trigger to flex said trigger end until it is no longer retained by said stop, whereby to permit pivotal movement of said trigger and consequent release of said latch and operation of said controlled means.

12. The invention as claimed in claim 11, in which said controlled means is a spring which is maintained by said latch in stressed condition.

13. The invention as claimed in claim 11, in which said operating means includes a diaphragm.

14. The invention as claimed in claim 11, in which cam means are provided to prevent accidental flexing of said one end of said trigger. 

1. A parachute release mechanism, which comprises: wall means to define first and second chambers, restricted communication means to effect restricted communication between said first chamber and the ambient atmosphere and to effect restricted communication between said second chamber and the ambient atmosphere, the volumes of said first and second chambers, and the flow characteristics of said restricted communication means, being such that a predetermined relationship is maintained between the air pressure in said first chamber and the air pressure in said second chamber as the parachute release mechanism falls through the atmosphere, the volumes of said first and second chambers, and the flow characteristics of said restricted communication means, also being such that the falling of the parachute release mechanism through the atmosphere at at least a predetermined dropping velocity for at least a predetermined distance effects predetermined lowering of the air pressure in said first chamber relative to the air pressure of the ambient atmosphere, and also effects predetermined lowering of the air pressure in said second chamber relative to the air pressure of the ambient atmosphere, pressure-responsive valve means to effect relatiVely unrestricted communication between said first chamber and the ambient atmosphere when the parachute release mechanism is at a predetermined set altitude, and mechanical actuating means responsive to the increased pressure in said first chamber, upon opening of said pressure-responsive valve means after dropping of the parachute release mechanism to said set altitude, and also responsive to achievement of said predetermined lowering in the air pressure in said second chamber, to effect opening of a parachute.
 2. The invention as claimed in claim 1, in which said predetermined relationship, maintained between the air pressure in said first chamber and the air pressure in said second chamber, is such that said actuating means will not operate when said pressure-responsive valve means is in closed condition, and in which said pressure-responsive valve means is in closed condition when above said set altitude, and is in open condition when below said set altitude.
 3. The invention as claimed in claim 1, in which said predetermined relationship, maintained between the air pressure in said first chamber and the air pressure in said second chamber, is such that the air pressure in said first chamber is maintained substantially equal to the air pressure in said second chamber while said mechanism is dropping through the atmosphere, in which said actuating means comprises a diaphragm one side of which is exposed to the air pressure in said first chamber, and the other side of which is exposed to the air pressure in said second chamber, and in which resilient means are provided to prevent operation of said diaphragm unless the pressure in said first chamber is a predetermined amount greater than the pressure in said second chamber.
 4. The invention as claimed in claim 1, in which said pressure-responsive valve means is closed at all altitudes above said set altitude, and is open at all altitudes below said set altitude, whereby to effect relatively unrestricted communication between the ambient atmosphere and said first chamber at said set altitude and at all altitudes lower than said set altitude, and in which said restricted communication means comprises a first capillary passage extending directly between said first chamber and the ambient atmosphere and further comprises a second capillary passage extending directly between said second chamber and the ambient atmosphere.
 5. The invention as claimed in claim 1, in which the volume of said first chamber is substantially equal to the volume of said second chamber, in which said restricted communication means comprises a first capillary passage extending directly between said first chamber and the ambient atmosphere and further comprises a second capillary passage extending directly between said second chamber and the ambient atmosphere, and in which the flow characteristics of said first capillary passage are substantially equal to the flow characteristics of said second capillary passage.
 6. The invention as claimed in claim 1, in which the volumes of said first and second chambers, and the flow characteristics of said restricted communication means, are such that the falling of said parachute release mechanism through the atmosphere at a velocity less than said predetermined dropping velocity does not effect said predetermined lowering of the air pressures in said chambers, and therefore does not result in operation of said actuating means upon operation of said pressure-responsive valve means at said set altitude, regardless of the distance of dropping.
 7. The invention as claimed in claim 1, in which said predetermined distance is at least sufficiently great to insure that said parachute will not be caught on the aircraft.
 8. The invention as claimed in claim 1, in which said pressure-responsive valve means is an aneroid valve.
 9. The invention as claimed in claim 1, in which said actuating means comprises a trigger, a latch operated by said trigger, a compressed spring released in responsE to operation of said latch, and a diaphragm means one side of which communicates with said first chamber and the other side of which communicates with said second chamber, said diaphragm means being adapted to operate said trigger.
 10. The invention as claimed in claim 1, in which said actuating means includes a diaphragm the diameter of which is small in comparison to the volumes of said chambers, one side of said diaphragm communicating with said first chamber, the other side of said diaphragm communicating with said second chamber, and means operated by said diaphragm to effect opening of said parachute.
 11. A release mechanism, which comprises: a housing, a stop provided in said housing, a trigger pivotally mounted in said housing for pivotal movement about a predetermined axis, at least one end of said trigger being flexible, at least part of said one end of said trigger being inclined, said inclined part of said one end being adapted when said trigger is pivoting in a mechanism-cocking direction to cam relative to said stop to thereby flex said trigger end and permit trigger movement to a cocked position against one side of said stop, a latch operably associated with said trigger for retention thereby when said trigger is in said cocked position, controlled means operably associated with said latch for operation thereby, and operating means to push against said one end of said trigger to flex said trigger end until it is no longer retained by said stop, whereby to permit pivotal movement of said trigger and consequent release of said latch and operation of said controlled means.
 12. The invention as claimed in claim 11, in which said controlled means is a spring which is maintained by said latch in stressed condition.
 13. The invention as claimed in claim 11, in which said operating means includes a diaphragm.
 14. The invention as claimed in claim 11, in which cam means are provided to prevent accidental flexing of said one end of said trigger. 